/*
 * Copyright 2011 The IEC61850bean Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */
package com.beanit.josistack;

import com.beanit.jositransport.*;

import javax.net.ServerSocketFactory;
import java.io.IOException;
import java.net.InetAddress;
import java.nio.ByteBuffer;
import java.util.concurrent.TimeoutException;

/**
 * This class implements the server Service Access Point (SAP) for the Application Control Service
 * Element (ACSE) protocol as defined by ISO 8650 or ITU X.217/X.227. The ACSE provides services for
 * establishing and releasing application-associations. The class also realizes the lower ISO
 * Presentation Layer as defined by ISO 8823/ITU X226 and the ISO Session Layer as defined by
 * 8327/ITU X.225.
 */
public final class ServerAcseSap implements TConnectionListener {
    public ServerTSap serverTSap = null;
    public byte[] pSelLocal = ClientAcseSap.P_SEL_DEFAULT;
    private AcseAssociationListener associationListener = null;

    /**
     * Use this constructor to create a server ACSE SAP that listens on a fixed port.
     *
     * @param port                the local port listen on
     * @param backlog             the backlog
     * @param bindAddr            the InetAddress to bind to
     * @param associationListener the AssociationListener that will be notified when remote clients
     *                            have associated. Once constructed the AcseSAP contains a public TSAP that can be accessed
     *                            to set its configuration.
     */
    public ServerAcseSap(int port, int backlog, InetAddress bindAddr, AcseAssociationListener associationListener) {
        this(port, backlog, bindAddr, associationListener, ServerSocketFactory.getDefault());
    }

    /**
     * Use this constructor to create a server ACSE SAP that listens on a fixed port. The server
     * socket is created with the given socket factory.
     *
     * @param port                the local port listen on
     * @param backlog             the backlog
     * @param bindAddr            the InetAddress to bind to
     * @param associationListener the AssociationListener that will be notified when remote clients
     *                            have associated. Once constructed the AcseSAP contains a public TSAP that can be accessed
     *                            to set its configuration.
     * @param serverSocketFactory the server socket factory to create the socket
     */
    public ServerAcseSap(int port, int backlog, InetAddress bindAddr,
                         AcseAssociationListener associationListener, ServerSocketFactory serverSocketFactory) {
        this.associationListener = associationListener;
        serverTSap = new ServerTSap(port, backlog, bindAddr, this, serverSocketFactory);
    }

    /**
     * Start listening for incoming connections. Only for server SAPs.
     *
     * @throws IOException if an error occures starting to listen
     */
    public void startListening() throws IOException {
        if (associationListener == null || serverTSap == null) {
            throw new IllegalStateException("AcseSAP is unable to listen because it was not initialized.");
        }
        serverTSap.startListening();
    }

    public void stopListening() {
        serverTSap.stopListening();
    }

    /**
     * This function is internal and should not be called by users of this class.
     */
    @Override
    public void serverStoppedListeningIndication(IOException e) {
        associationListener.serverStoppedListeningIndication(e);
    }

    /**
     * This function is internal and should not be called by users of this class.
     */
    @Override
    public void connectionIndication(TConnection tConnection) {
        try {
            AcseAssociation acseAssociation = new AcseAssociation(tConnection, pSelLocal);
            ByteBuffer asdu = ByteBuffer.allocate(1000);
            try {
                asdu = acseAssociation.listenForCn(asdu);
            } catch (IOException e) {
                // Server: Connection unsuccessful.
                tConnection.close();
                return;
            } catch (TimeoutException e) {
                // Illegal state: Timeout should not occur here
                tConnection.close();
                return;
            }
            associationListener.connectionIndication(acseAssociation, asdu);
        } catch (Exception e) {
            // Association closed because of an unexpected exception.
            tConnection.close();
        }
    }
}
